Tendon injuries are very common. Sprains will heal spontaneously, but complete tears will often lead to disability if not surgically treated. Despite surgical repairs, about 15% of Achilles tendons and 40% of two tendon rotator cuff repairs subsequently fail. Furthermore, the repaired tendons seldom return to pre-injury strength and function levels. Attempts to improve the success rate have involved better suture and bone anchors, new surgical methods, and patches to reinforce the repair and provide scaffolding for tissue ingrowth to thicken the tendon. There are also reports of improved tendon healing using growth factors such as BMP-2, BMP-12, PDGF-BB, and bFGF in preclinical models.
Although some researchers have indicated tendon as a possible tissue to grow using mesenchymal stem cells (MSC), very little work has been done along that line. There is even less work reported with adipose- or other microvascular tissue-derived stem or progenitor cells. It has been shown that fresh cells from adipose and other microvascular tissues could be used for regenerating orthopedic tissues. Others have since shown that these cells help treat tendon lesions in horse models of tendon injury, as well as other conditions. These cells were always autologous or syngeneic.
However, the use of autologous sourced stem cells is inconvenient. It requires two surgical procedures with associated pain, cost, and morbidity. There are also risks in shipping the tissue to the lab for processing and a delay in treatment of the injury or disease.
Recently bone graft products have been launched that use uncultured bone marrow cells from allogeneic donors adsorbed to bone chips or demineralized bone matrix (DBM). However, this type of product is unsuitable for soft-tissue repair and requires special handling to preserve the bone marrow cells.